Rolling mill roll and composition thereof



Patented Mar. 23, 1954 Martin Brezin, Munhall, Paradigms" to lifiit r States Steel Corporation, a corporation of New" J ersey N'o firawi'iigl Application Jeanne 2,1932, I

Serial No. 2641652 t 'bluiiiis. (Cl."'l5 1'28) This" in'ventiorfrlatsto "raring min rolls "arid more particularly to forged rolling mill rolls.

Rolling mill rolls such as are used in relatively wide present day tandem cold reduction mills are normally forged rolls since cast rolls will not withstand this type of service. On the other hand, it has heretofore been impossible to produce a forged roll having a sufiicient depth of hardness sufficient to eliminate the need for rehardening during the life of the roll. Rolls are ordinarily redressed several times, that is the outer surface ground off so that the nominal diameter thereof is reduced in total over 1". For instance a cold roll size ordinarily used is 21" which may be dressed down to 19%" during the so-called life thereof. Although it is highly desirable to have a depth of hardness suificiently deep that the outer surface can be removed to such depth without rehardening it has heretofore been necessary to reharden at least once since forged rolls could not be produced having a suflicient depth of hardness to permit dressing down more than a small amount without rehardening. Due to the nature of a forged steel roll, the problems involved are quite complex. Such rolls must have an extremely hard outer surface which hardness tapers ofi gradually inwardly of the roll and considerable residual stresses in the roll are involved which must be in delicate balance. If these stresses become unbalanced during hardening or through misuse, such rolls are subject to bursting with explosive force.

It is accordingly an object of the present invention to provide a forged steel roll having sufficient depth of hardness that rehardening is not necessary during the life thereof.

It is a, further object of the present invention to provide a stable forged rolling mill roll and analysis therefor.

I have discovered that the foregoing objects can be attained by the use of a high carbon steel having a minor nickel content along with chromium, molybdenum and vanadium.

The preferred composition of my improved roll is as follows:

Balance iron and residual impurities in common amounts.

A ranges rdllof su'cli cbmpositiori c'an ened to a Shore scleroscope hardness in excess of 90 to depth of over of an inch. Thus the roll need not be hardened even though 1 /2 is: ground off the diameter during the life thereof.

The foregoing composition is such that the hardening quench treatment can be relatively mild without resulting in untransformed austenite at the outer surface. When untransforced austenite is obtained, resort to transformation by freezing is necessary and this results in a change in the magnitude, and the direction of the residual stresses are altered to render the roll unstable and make it unsafe to use. With my improved composition containing a small amount of nickel, i. e., about .50% in conjunction with an alloy having a high carbon content, balanced stresses are obtained due to the fact that a relatively mild quench can be used.

As illustrative of the teachings of this: invention, a 21" roll was forged from steel containing .90% carbon, 35% manganese, .40% silicon, 55% nickel, 1.80% chromium, 20% molybdenum and .18% vanadium. After forging and while still hot, the roll is transferred to a spheroidizing furnace heated uniformly to 785 C., cooled to 600 C. at 5 C. per hour, cooled within the furnace to 200 C., and then allowed to cool at any desired rate, after which it is roughly machined. The roll is gradually and uniformly heated until its barrel reaches 910 C. After reaching this temperature, the roll is removed from the furnace, placed into a quenching jig and cooled with a water spray for 40 minutes to room temperature. The temperature of'the roll is subsequently equalized by holding for five hours in boiling water and then double tempered in a gas-fired furnace at l-190 C. This completes the thermal treatment which is followed by machining the journal and grinding the roll barrel to final dimensions.

After processing in the manner described, the roll had a Shore scleroscope hardness of 95-97 on the surface and 90 Share three-quarters of an inch below the surface. Conventional rolls have a hardness of Shore at the same distance from the surface.

While I have shown and described one specific embodiment of my invention, it will be understood that this embodiment is merely for the purpose of illustration and description and that various other forms may be devised within the scope of my invention, as defined in the appended claims.

I claim:

,1. A forged and hardened steel rolling mill roll containing .80 to .95% carbon, .40 to .70% nickel, .30 to 40% manganese, .30 to 50% silicon, 1.50 to 2.00% chromium, .15 to 25% molybdenum, .15 to .20% vanadium, balance iron and residual impurities in common amounts, said roll being characterized in the spheroidized and quenched condition by a Shore scleroscope hardness of at least 90 at a point three-quarters of an inch below the outer surface, balanced internal stresses and the absence of untransformed austenite adjacent the outer surface whereby the diameter of said roll may be reduced at least 1%" without requiring rehardening thereof.

2. A steel alloy composition for rolling mill rolls, said alloy consisting of .80 to .95% carbon, .40 to 370% nickel, .30 to .40% manganese, .30 to 50% silicon, 1.50 to 2.00% chromium, .15 to 25% molybdenum, .15 to .20% vanadium, balance iron and residual impurities in common amounts, said alloy being characterized by the 4 absence of untransformed austenite in the spheroidized and quenched condition and a Shore scleroscope hardness of at least 90 at a point three-quarters of an inch below the outer surface thereof in thick sections.

MARTIN BREZIN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,558,918 Peters Oct. 27, 1925 FOREIGN PATENTS Number Country Date 15,498 Great Britain of 1907 OTHER REFERENCES The Selection and Hardening of Tool Steels, page 13 6. Edited by Seabright. Published in 1950 by the McGraw-Hill Book Co., New York. 

1. A FORGED AND HARDENED STEEL ROLLING MILL ROLL CONTAINING .80 TO .95% CARBON, .40 TO .70% NICKEL, .30 TO 40% MANGANESE, .30 TO 50% SILICON, 1.50 TO 2.00% CHROMIUM, .15 TO 25% MOLYBDENUM, .15 TO .20% VANADIUM, BALANCE IRON AND RESIDUAL IMPURITIES IN COMMON AMOUNTS, SAID ROLL BEING CHARACTERIZED IN THE SPHEROIDIZED AND QUENCHED CONDITION BY A SHORE SCLEROSCOPE HARDNESS OF AT LEAST 90 AT A POINT THREE-QUATERS OF AN INCH BELOW THE OUTER SURFACE, BALANCED INTERNAL STRESSES AND THE ABSENCE OF UNTRANSFROMED AUSTENITE ADJACENT THE OUTER SURFACE WHEREBY THE DIAMETER OF SAID ROLL MAY BE REDUCED AT LEAST 11/2" WITHOUT REQUIRING REHARDENING THEREOF. 